It isn’t a simple matter to speak of the weather at ArteSumapaz. Basically, there are supposedly three seasons; rainy and dry and in-between. When it’s rainy, it tends to be more overcast, with about an hour of precipitation every day or night. For the most part, the center being at an elevation of 1,400 meters above sea level, is considered temperate. You might need a sweater or hoodie in the first couple hours of the morning, but by late morning, you might be down to a t shirt.
There are official charts of what to expect in Colombia, but they tend to be inaccurate perhaps because of global warming or the “el niño/la niña” (https://www.climate.gov/enso .) weather patterns. But what I can say is that our most rainy season, whenever that might be, tends to be pleasant.